1. Field
The present application relates to medical device implants. More particularly, the present application relates to devices for inserting a tubular medical device implant into the body (specifically, into the eye).
2. State of the Art
Glaucoma is a buildup of pressure in the eye which can impinge on the blood supply feeding the optic nerve. Such buildup of pressure in the eye, if left unchecked, can damage the optic nerve, resulting in vision loss and blindness. Various shunts and tools for shunts have been proposed for relieving the buildup of pressure.
U.S. Pat. No. 7,431,709 describes a glaucoma drainage shunt made from a soft material, e.g., SIBS. FIG. 1 shows the glaucoma drainage shunt 1 of U.S. Pat. No. 7,431,709, which includes a small tube 2 with a tab 3 located approximately halfway down the length of the tube. The lumen of the tube 2 is 50 to 100 μm in diameter. The tab 3 prevents migration of tube 2 into the eye, which can occur while blinking; that is, the eyelid pushes the tube into the eye.
The glaucoma drainage shunt 1 of FIGS. 1 and 2 minimizes the buildup of pressure in the eye for treatment of glaucoma. The glaucoma drainage shunt 1 is delivered into the eye such that the entrance to the tube the distal end (D) is in the anterior chamber of the eye and the proximal end (P), or drainage end of the glaucoma drainage shunt 1 is in a pocket or space between the conjunctiva/tenons and sclera wherein the space fills with drained aqueous humor and forms a blister-like reservoir called a bleb (FIG. 2). Aqueous humor can accumulate in the bleb and diffuse through the conjunctiva to the tear film and tear ducts or through the sclera into the venous system of the eye. In this manner, aqueous humor is removed from the anterior chamber and into the bleb where it diffuses out and the intraocular pressure (IOP) in the anterior chamber is thereby reduced, thereby arresting glaucoma.
In order to facilitate placing the glaucoma drainage shunt in the eye, an inserter, described in FIG. 9 of the U.S. Pat. No. 7,431,709 was developed. This inserter 31, reproduced from the U.S. Pat. No. 7,431,709 here as FIGS. 3A and 3B, is comprised of a handle 32 and a slotted needle 33 that slidely fits within outer needle 34. Thumb slide 35 is rigidly attached to slotted needle 33. The glaucoma drainage shunt 1 is loaded in slotted tip 33 of the inserter 31, as shown in the enlarge tip in FIG. 3B. The tab 3 sticks out from a slot 36 in the slotted tip 33 of inserter 31.
A needle tract is first made in the eye in the area where the glaucoma drainage shunt 1 is to be placed. The slotted tip 33 of inserter 31, which contains the glaucoma drainage shunt 1, is inserted into the needle tract until tab 3 rests against the needle tract entrance; i.e., the sclera of the eye. The thumb slide 35, attached to slotted tube 33 is then pulled backwards relative to the glaucoma drainage shunt, which is held stationary by means of tab 3 resting against outer, stationary tube 34, and the slotted needle 33 is retracted, leaving the glaucoma drainage shunt 1 behind in the needle tract of the eye. FIG. 2 shows the glaucoma drainage shunt 1 in its final resting position in the eye. A needle tract is preferably made first as it can be difficult to insert the slotted tube 33 in the eye due to part of the cutting tip of the tube (needle) being removed to accommodate the slot, which accommodates the tab 3.
There are several problems associated with the inserter 31 of FIG. 3A used in conjunction with the glaucoma drainage shunt 1 of FIGS. 1 and 2. The inserter 31 is large and quite often the patient's nose or forehead is in the way and the inserter tip 33 cannot be maneuvered into the proper position to follow the needle tract. Bending the needle to allow a better approach prevents slotted tube 33 from sliding in outer tube 34; therefore the needle assembly cannot be bent. Also, the SIBS material of the glaucoma drainage shunt is soft and sticky (having a durometer of Shore 10A to 60A) and does not slide well in the slotted needle of the inserter and often jams, which delays the insertion procedure or can damage the shunt. Moreover, tissue can protrude into slot 33 of the inserter, binding the glaucoma drainage shunt and causing it to buckle when inserted in the needle tract. Further, the outer diameter of the inserter needle is large and stretches the needle tract. When the needle tip is in the needle tract, fluid can flow around the glaucoma drainage shunt and within the needle lumen and deflate the eye (i.e., a condition termed “hypotony”), which can lead to adverse events including retinal detachment, and the like. Also, tab 3 of the glaucoma drainage shunt 1 may at times rotate upward like the dorsal fin on a shark; when this occurs, the tab 3 can erode through the conjunctiva and cause infections.
The tab 3 of the glaucoma drainage shunt 1 was designed to work in tandem with slotted tube 33 of the inserter device 31. Over time, the design of the glaucoma drainage shunt was changed to shunt 41 as shown in FIG. 4 where the tab 43 is made symmetrical and atraumatic so as not to erode through the conjunctiva.
Also, the glaucoma drainage shunt 41 can be introduced into the needle tract with a forceps 50 into the eye as shown in FIG. 5. However, there are problems associated with using a forceps. For example, inserting the glaucoma drainage shunt 41 into the needle tract with the forceps 50 is difficult because as the glaucoma drainage shunt 41 is floppy and can buckle. The insertion of the glaucoma drainage shunt 41 is slow and unpredictable because the glaucoma drainage shunt 41 buckles when pushed from its proximal end and, thus, has to be incrementally pushed from the section of the tube near the entrance to the needle tract.
Another arrangement for inserting the drainage shunt 41 is shown in FIG. 6, which shows the glaucoma drainage shunt 41 of FIG. 4 in conjunction with a wire stylet 60 connected to handle 61. The stylet 60 passes through the lumen of the tube of the shunt 41. There are also numerous problems with using the arrangement shown in FIG. 6. Although the stylet 60 helps stiffen the tube, the stylet 60 is made from a very small diameter wire, in the order of 70 μm, which renders it inadvertently sharp and it often lodges in the fibrous tissue of the needle tract, preventing insertion of the glaucoma drainage shunt 41 into the needle tract. In addition, the soft tube of the shunt 41 is prone to collapsing, accordion-like, over the stylet 60, which prevents insertion of the shunt 41 into the needle tract. Lastly, the stylet 60 often adheres to the lumen of the shunt 41 and thus is difficult to remove from the shunt 41 without dislodging the shunt.
In yet another example, FIGS. 7A to 7D show an alternate approach where the glaucoma drainage shunt 41 of FIG. 5 is used in conjunction with an assembly 70 that includes a trocar 74 that extends over a needle 71. Specifically, the assembly 70 includes a hypodermic-type needle 72 extending from a hub 71. The needle 72 has a sharpened end 72 that is inserted into the eye 73. The trocar 74 is a thin-walled over-tube with a beveled distal end. A slot 75 is formed through the sidewall of the trocar 74 at its distal end and extends proximally in a direction parallel to the central axis of the tube 74. The trocar 74 can be made from metal or a hard plastic, such as polyimide. The needle shaft extends through the lumen of the over-tube 74 and is configured so that the sharp end 72 of the needle shaft extends beyond the beveled distal end of the over-tube 74 as shown in FIG. 7A. In this configuration, the sharp end 72 of the needle shaft is used to penetrate the eye and form a needle tract leading into the eye. The beveled distal end of the trocar 74 passes through the needle tract and enters the eye as the assembly (trocar and needle) are pushed into the eye, thereby enlarging the needle tract slightly. The needle 70 is then removed leaving the trocar 74 behind as shown in FIG. 7B. Glaucoma drainage shunt 41 is then inserted into slot 75 of trocar 74 with a forceps (not shown) as depicted in FIG. 7C. The trocar 74 is then removed leaving the glaucoma drainage shunt 41 behind and passing through the tract into the eye as shown in FIG. 7D.
There are problems associated with the approach of FIGS. 7A to 7D. First, it is difficult to push the needle 71 in place with the trocar 74 on the needle 71. Secondly, when the needle 70 is removed from the trocar 74 to leave behind the trocar 74 passing through the tract (FIG. 7B), aqueous humor leaks through the trocar 74, which can allow for unwanted deflation of the eye (i.e., a condition termed “hypotony”). Thirdly, when the trocar 74 is removed from the eye to leave behind the shunt 41 passing through the tract (FIG. 7D), the trocar can drag the glaucoma drainage shunt 41 out with it.
An alternate arrangement to that shown in FIGS. 7A to 7D (not shown) was attempted where the needle tract was made first with a sharp needle, then the glaucoma drainage shunt, which was preloaded with the glaucoma tube in a sharp metal trocar was inserted into the needle tract. The glaucoma drainage shunt was held with a forceps and the trocar removed. The problem with this alternate arrangement is that the glaucoma drainage shunt often came out with the trocar. In addition, aqueous humor leaked around the glaucoma drainage shunt and the eye deflated.